Listed among the contraindications to NIPPV in this and other reviews is impaired level of consciousness. However, its use in hypercapnic RF with decreased LOC is common. Concerning that, the review says:
Patients with altered levels of consciousness due to hypercapnic ARF associated with COPD exacerbation are exposed to high risk of NIV failure, but a cautious attempt with NIV may be performed in these patients, provided that a careful monitoring is available and prompt ETI is accessible . In treatment-responsive patients, recovery of consciousness occurs within 45–60 min after NIV application.